1. Field of the Invention
The present invention relates to a lens, and more particularly, to a lens having a supercritical fluid.
2. Discussion of the Related Art
Various conventional products, such as cameras, projectors, and laser printers, adopting a lens need a focusing or zooming function of the lens from the characteristic point of view. In the past, a method of moving a lens, to focus or zoom the lens, was normally used. Recently, however, a method of changing the shape of a lens has been proposed with the development of various technologies.
When using this conventional method of moving the lens to focus or zoom the lens, a drive unit for driving the lens is required, and a large space necessary to drive the lens must be secured. The zooming function for moving the lens is performed by the operation of a motor. Consequently, the power consumption is increased, and therefore, a battery is rapidly exhausted. In order to solve the above-mentioned problems, i.e., to minimize the increase of the size and the power consumption, there has been carried out research on a method of changing the shape of a lens itself, instead of moving the lens, to accomplish the zooming function of the lens.
Changing the shape of the lens may be accomplished by using a micro electro mechanical system (MEMS) technology or by using a liquid as the lens. In the MEMS technology, the lens is divided into several lens sections, and the divided lens sections are separately controlled to diffract light and thus adjust the magnifying power. For the MEMS technology, the lens is divided into a limited number of lens sections, with the result that the characteristics of the lens may be partially restricted. For the liquid lens, on the other hand, the lens may be affected by an external force, such as gravity, or the safety of the lens may not be guaranteed.
The conventional method of using the liquid as the lens has been generally carried out based on a volume change type method in which a liquid is stored in a transparent film, and the volume of the transparent film is changed to change the focal distance of the lens, or an electrowetting type method in which a hemispherical liquid lens is formed on an electrode, and voltage is applied to the liquid lens to change the focal distance of the liquid lens. Recently, the electrowetting type method has attracted considerable attention.
FIGS. 1A and 1B are sectional views illustrating a conventional electrowetting type lens. Hereinafter, the conventional electrowetting type lens will be described with reference to FIGS. 1A and 1B.
As shown in FIGS. 1A and 1B, a barrier, which is constituted by an insulation film 12 and an electrode 13, is formed on a substrate 14, which is made of glass. A conductive aqueous liquid 15 and a nonconductive oily liquid 16 are injected into the insulation film 12, and a hydrophobic coating film 11 is formed to cover the conductive aqueous liquid 15 and the nonconductive oily liquid 16 in a sealed state. At this time, the spherical interface between the conductive aqueous liquid 15 and the nonconductive oily liquid 16 serves as a lens. When voltage is not applied to the conductive aqueous liquid 15 and the nonconductive oily liquid 16, the interface between the conductive aqueous liquid 15 and the nonconductive oily liquid 16 takes a shape as shown in FIG. 1A. When voltage is applied to the conductive aqueous liquid 15 and the nonconductive oily liquid 16, the interface between the conductive aqueous liquid 15 and the nonconductive oily liquid 16 becomes flat, and then takes a shape as shown in FIG. 1B.
When voltage is not applied to the conductive aqueous liquid 15 and the nonconductive oily liquid 16, as shown in FIG. 1A, the interface between the conductive aqueous liquid 15 and the nonconductive oily liquid 16 serves as a concave lens. When voltage is applied to the conductive aqueous liquid 15 and the nonconductive oily liquid 16, as shown in FIG. 1B, molecules of the conductive aqueous liquid 15 move toward the electrode 13 while the molecules of the conductive aqueous liquid 15 have a polarity. As a result, the interface between the conductive aqueous liquid 15 and the nonconductive oily liquid 16 changes into a shape as shown in FIG. 1B. Consequently, the interface between the conductive aqueous liquid 15 and the nonconductive oily liquid 16 serves as a convex lens for converging incident beams into one point.
As described above, it is possible to control the interface between the two liquids by adjusting voltage applied to the conductive liquid, thereby adjusting the focal distance of the lens without the mechanical movement of the lens. In the conventional electrowetting type lens, however, it is required that the voltage be applied to the conductive liquid at room temperature and atmospheric pressure, with the result that the efficiency of the lens is still a serious problem.